Post-mixed oxy-fuel oxide reduction



Jan. 21, 1964 J. w. R055 3,118,758

POST-MIXED OXY-FUEL. OXIDE REDUCTION Filed March 27, 1961 NATURAL OXIDE oXYGEN 2 2 1 1- 1- f l I I f /ZZ INVENTOR. JOHN W. ROSS hwzxwg,

A 7' TORNE V United States Patent 3 118 758 PGST-MIXED oxY-rnni. oxrnn REnUc-rioN John W. Ross, Toronto, Gntario, Canada, assignor to Union Carbide Canada Limited, a corporation of Toronto, Ontario, Canada Filed Mar. 27, 1961, Ser. No. 98,694 9 Claims. (Cl. 7526) This invention relates to post-mixed oxy-fuel oxide reduction, and more particularly, to oxygen-natural gas burners and methods for the direct reduction of iron ore.

For this purpose, it has been proposed to oxidize finely ground magnetite concentrate to hematite in an oxidizing flame, and reduce the hematite to molten iron in a cracked natural 'gas atmosphere, all in a single furnace. This required the burner to produce the initial oxidizing and also heat the furnace and preheat the feed.

The initial reaction, that of oxidizing the magnetite (Fe O into hematite (Fe O requires a gas mixture of at least two parts oxygen to one part natural gas. Such a mixture, if mixed before ignition, as in a pre-mix system, will very likely flash back, i.e., the flame will back up into the gas tubes, causing damage to the equipment. l re-nix burners cannot be operated consistently with oxy-fuel gas ratios of 2:1 or greater The main objects of the invention are therefore to avoid these difficulties, to eliminate flashbacks, and to prevent damage to the equipment.

According to the present invention, method and apparatus are provided for post-mixed oxy-fuel direct oxide reduction, which comprises passing oxygen through a manifold and tubes converging therefrom into contacting relation in a nozzle, discharging the oxygen from said nozzle into a combustion zone outside of said nozzle, passing fuel gas into a chamber surrounding said converging tubes to pass through the interstices therebetween in said nozzle into said combustion zone, and passing oxide through a central tube to pass inside said contacting tubes in said nozzle into said combustion zone.

The fuel is preferably natural gas at a ratio of two to one or higher. The manifold, tubes and nozzle are preferably of Inconel construction, and the incoming gas supplies are preferably preheated to 1000 F.

Preferably, the tubes in the nozzle form a hexagonal 1 cluster, and at least the lower end portion of the central \oxide tube is swaged to hexagonal form. The openings in the oxygen tubes are preferably spudded to distribute pressure in the oxygen chamber.

Inthe drawings:

l FIGURE 1 is an elevation, partly in section, of a biurner apparatus according to and for carrying out the ijnethotl of, the preferred embodiment of the present in- \Yention;

FIGURE 2 is a horizontal section taken along the line 2-2 of FIG. 1 showing a top plan of the header plate;

1 FIGURE 3 is a bottom plan view looking in the direction of the arrows 33 of FIG. 1 and FIGURE 4 is an enlarged detailed cross section through the inlet orifice of an oxygen tube.

In the form shown, the burner is constructed of Inconel with Heliarc welding or silver soldering, and comprises a casing divided by a header plate 12 into an upper oxygen chamber 14 and a lower natural gas chamber 16. The chamber 14 has a top plate 15 provided with an oxygen inlet 18, and the chamber 16 has a cylindrical wall 19 provided with a natural gas inlet 20.

A plurality of oxygen tubes 22 have their upper ends installed in the header plate 12 in substantially uniformly spaced relation. As shown in FIG. 4, the oxygen tubes preferably project above the header plate 12, and the ice openings in the tubes are spudded with copper plugs 23 secured inside the tube ends, and thereafter drilled to a precision diameter.

The tubes 22 converge downwardly into contacting relation as a hexagonal cluster as they pass through a central aperture in the bottom plate 24 of the casing and extend out therebelow. The casing 10 has a hexagonal sleeve 25 secured thereto surrounding the aperture and confining the tubes extending therethrough and coextensive with the tubes.

An oxide tube 26 passes down through the center of the top plate 15 and header plate 12, and has at least the lower end thereof swaged'to hexagonal cross section, to pass through the hexagonally nested tubes in theinside of the hexagonal sleeve 25and coextensive therewith to form therewith an outlet nozzle. After assembly, the tubes 22 and 26 are cut off flush with the bottom of the sleeve 25, and burrs removed.

In operation, the oxygen is fed through the inlet 18 into the chamber 14 which acts as a manifold for the tubes 22. The natural gas passes through the interstices of the cluster of oxygen and powder tubes to the com bustion area immediately below the nozzle 25. The oxide is introduced by gravity through the tube 26 and passes through the hexagonal lower end thereof inside the nested oxygen tubes to the combustion zone.

The inlet openings of the oxygen tubes being spudded, distribute the pressure in the oxygen manifold. The oxygen to natural gas ratio must be at least 2:1 in order to obtain the proper oxidizing flame. The ratio can go as high as 4:1 with the post-mix type of burner. The actual volumes of gas used can vary widely but 3,000 c.f.h. oxygen and 1,400 c.f.h. natural gas is used in the lb./ hr. pilot furnace.

The composition of the combustion gases is about 55% hydrogen, 34% carbon monoxide and residual quantities or carbon dioxide and methane. The magnetite influent has been ozidized to hematite.

What is claimed is:

l. Post-mixed oxy-fuel method of direct oxide reduction, which comprises passing oxygen into a manifold, taking off separate streams of oxygen from said manifold in uniformly spaced relation through tubes leading therefrom and converging into contacting relation with each other inside a nozzle confining the same, discharging the oxygen from said contacting tubes as a ring of justaposed streams into a combustion zone outside of said nozzle, passing fuel gas into a chamber surrounding said tubes to pass through the interstices between said contacting tubes and said confining nozzle, discharging said fuel gas from said interestices as a ring of juxtaposed streams of fuel gas concentric with said ring of oxygen streams and respectively interposed between the streams thereof, whereby the effluent gases form a ring of post-mixed flames in said combustion zone, passing oxide through a central tube to pass inside said contacting tubes in said nozzle, and discharging said oxide from said central tube through the center of said ring of post-mixed flames into said combustion zone.

2. Method as claimed in claim 1, in which said manifold, tube and nozzles are of inconel construction, and the incoming gas supplies are preheated to 1000 F.

3. Method as claimed in claim 1, in which the oxide is iron ore, and the fuel is natural gas at a ratio of above about two to one.

4. Post-mixed oxy-fuel burner and oxide reduction apparatus comprising a casing, a header plate dividing said casing into an upper oxygen chamber and a lower fuel gas chamber, oxygen tubes having their upper ends installed in said header plate in substantially uniformly spaced apart relation, said tubes converging down into contacting relation and passing out of the bottom of said casing,

a central oxide tube passing through the top of said casing and said header and inside said contacting tubes, means for supplying oxygen to said oxygen chamber to pass through said tubes, means for supplying fuel gas to said fuel gas chamber to pass through the interstices between said tubes, and means for supplying oxide to the top of said central oxide tube to pass inside said contacting oxygen tubes.

5. Post-mixed oxy-fuel burner and oxide reduction apparatus as claimed in claim 4, in which the burner is constructed of Inconel.

6. Post-mixed oxy-fuel burner and oxide reduction apparatus claimed in claim 4, in which said contacting tubes form a hexagonal cluster.

7. Post-mixed oxy-fuel burner and oxide reduction apparatus as claimed in claim 4, in which at least the lower end of said central oxide tube is swaged to hexagonal form.

8. Post-mixed oxy-fuel burner and oxide reduction apparatus as claimed in claim 4, in which the upper ends of said oxygen tubes extend above said header plate, and are spudded to a precision diameter.

9. Apparatus for post-mixed oxy-fuel direct oxide reduction, which comprises a manifold, tubes leading from said manifold, a nozzle confining said tubes, means for passing oxygen into said manifold, means for taking off separate streams of oxygen from said manifold in uniformly spaced relation through said tubes, said tubes converging into contacting relation with each other inside said nozzle, means for discharging the oxygen from said contacting tubes as a ring of juxtaposed streams into a combustion zone outside of said nozzle, means for passing fuel gas into a chamber surrounding said tubes to pass through the interstices between said contacting tubes and said confining nozzle, means for discharging said fuel gas from said interstices as a ring of juxtaposed streams of fuel gas concentric with said ring of oxygen streams and respectively interposed between the streams thereof, whereby the effiuent gases form a ring of post-mixed flames into said combustion zone, means for passing oxide through a central tube to pass inside said contacting tubes in said nozzle, and means for discharging said oxide from said central tube through the center of said ring of post-mixed flames into said combustion zone.

References Cited in the file of this patent UNITED STATES PATENTS 

4. POST-MIXED OXY-FUEL BURNER AND OXIDE REDUCTION APPARATUS COMPRISING A CASING, A HEADER PLATE DIVIDING SAID CASING INTO AN UPPER OXYGEN CHAMBER AND A LOWER FUEL GAS CHAMBER, OXYGEN TUBES HAVING THEIR UPPER ENDS INSTALLED IN SAID HEADER PLATE IN SUBSTANTIALLY UNIFORMLY SPACED APART RELATION, SAID TUBES CONVERGING DOWN INTO CONTACTING RELATION AND PASSING OUT OF THE BOTTOM OF SAID CASING, A CENTRAL OXIDE TUBE PASSING THROUGH THE TOP OF SAID CASING AND SAID HEADER AND INSIDE SAID CONTACTING TUBES, MEANS FOR SUPPLYING OXYGEN TO SAID OXYGEN CHAMBER TO PASS THROUGH SAID TUBES, MEANS FOR SUPPLYING FUEL GAS TO SAID FUEL GAS CHAMBER TO PASS THROUGH THE INTERSTICES BETWEEN SAID TUBES, AND MEANS FOR SUPPLING OXIDE TO THE TOP OF SAID CENTRAL OXIDE TUBE TO PASS INSIDE SAID CONTACTING OXYGEN TUBES. 